This invention relates to a process for drying juice products to provide improved non-hygroscopic, free-flowing food and/or beverage powders. More particularly, the invention relates to a hydration drying process for producing dried fruit, vegetable or botanical powders which are free-flowing, non-hygroscopic and upon reconstitution in a liquid such as water are characterized by their excellent quality, color, viscosity, fragrance, palatability and their freedom from "air sols" and surface foam.
This invention also has application to the production of non-food and/or non-beverage products of a composite character, wherein the components are water-soluble, water-absorptive or water dispersible.
When referring to a fruit, vegetable or botanical powder in the title and specification, it will be recognized that by "powder" is meant a subdivided solid material that has so little free moisture that it is free-flowing and can be readily spooned from a jar or other container. No specific particle size is to be implied other than that it be such that the material is free-flowing and will dissolve to a large extent in a liquid such as water within a reasonable period of time. The term "reconstitution" as used herein, relates to the mixing of a dried fruit, vegetable and/or botanical powder with a liquid such as hot or cold water, milk, or in some cases with semi-liquid or other food ingredients, to produce a reconstituted product. The reconstituted product may be a juice beverage, concentrate, sauce, pudding, soft drink or a puree, and may be derived from natural, commercially-available fruits and/or vegetables and/or botanical plants. The term "Brix" is a common unit of measurement to express the concentration of dissolved solids in an aqueous solution and has been specified as the unit to be used in all Food and Drug Administration, U.S. Department of Agriculture and the Florida Citrus Code for fruit products and particularly for concentrated fruit juices.
Fresh fruit juices typically contain about 84-92% of water. This high water content places a heavy burden on the packaging, handling, storing and shipping of such juices and has stimulated the development of many processes for the partial or complete dehydration of such juices. Conventional processes include spray drying, vacuum shelf or belt drying, drum drying, foam-mat drying and freeze drying. These processes generally involve the concentration of juice followed by the dehydration of the concentrate through the application of heat and/or vacuum under controlled conditions. Many difficulties have been encountered in such processes, especially those processes yielding dry, solid products, and heretofore there has been developed no practical and economical process for the production of free-flowing juice powders that can be readily reconstituted by the addition of a liquid to yield a product closely resembling a fresh juice beverage in quality, flavor and appearance.
Spray drying is not satisfactory in many cases because, as a result of the drastic heating conditions generally required, the dried product is usually found to be inferior to the original juice concentrate in flavor and stability. Also, such products are extremely hygroscopic, due partly to the natural hygroscopicity of juice solids and partly to the caramelization which takes place as a result of the heating. In many cases, it is difficult to spray dry the juices without the addition of large amounts of carriers. If used, these carriers can impart an undesirable taste to the product and are generally unacceptable at the concentration levels that are required for satisfactory spray drying.
Vacuum shelf or belt drying also imparts cooked flavor to the dried product and frequently causes caramelization of the product. This results in an undesirable taste and detracts from visual acceptance. Moreover, because of the high vacuum conditions of these drying processes, desirable volatiles are lost through vaporization.
In drum drying, the sugar present in the juice prevents the formation of a sheet which can be easily removed by the dryer's doctor blade or scraper. Instead of being able to remove a continuous dried sheet from the dryer, the dried juice yields a gummy mass after heating which collects at the doctor blade and disrupts the drying operation. This process also imparts an undesirable off-flavor to the product.
Foam-mat drying involves the use of a foaming agent in the juice during drying. This foaming agent causes formation of extremely small, microscopic bubbles and produces a larger surface for rapid and more complete drying of the juice powders. However, this process is unsatisfactory since the powders produced often contain incorporated microscopic air bubbles which can be detrimental to the flavor and stability of the powder. Upon reconstitution, "air sols" or colloidal dispersions of these air bubbles are formed throughout the solution. These bubbles impart to the reconstituted juice an unnatural, white, cloudy or milky appearance. After the reconstituted product stands a very short time, the "air sols" rise and collect on the surface as a dense layer of foam. The presence of this milky appearance and particularly the presence of the foam are detrimental to the physical appearance of the product and adversely affect their commercial acceptance.
Freeze drying in general produces the most acceptable product of conventional drying processes. However, the slow rate of sublimation from the frozen state and the high vacuum associated with the process result in loss of desirable volatiles through vaporization and make the process relatively expensive. Also, the dried product produced is hygroscopic and this adversely affects the storage stability and spoonability of the dried product.
In comparison to the present invention, major difficulties encountered in the foregoing conventional drying processes are (1) higher costs; (2) greater loss of volatile constituents during the drying process; and (3) development of undesirable off-flavors during the drying process, usually because of heat.